We aim to investigate the hemodynamics in focal steatosis and focal spared lesion of the liver using contrast-enhanced ultrasonography (CEUS) with Sonazoid. The subjects were 47 patients with focal steatosis and focal spared lesion. We evaluated enhancement patterns (hyperenhancement, isoenhancement, and hypoenhancement) in the vascular phase and the presence or absence of a hypoechoic area in the postvascular phase for these lesions using CEUS. Of the 24 patients with focal steatosis, the enhancement pattern was isoenhancement in 19 and hypoenhancement in 5. Hypoechoic areas were noted in the postvascular phase in 3 patients. Of the 23 patients with focal spared lesions, the enhancement pattern was isoenhancement in 18 and hyperenhancement in 5. No hypoechoic areas were noted in the postvascular phase in any patient. The hemodynamics in focal steatosis and focal spared lesions in nondiffuse fatty liver can be observed using low-invasive procedures in real-time by CEUS. It was suggested that differences in the dynamics of enhancement in the vascular phase of CEUS were influenced by the fat deposits in the target lesion, the surrounding liver parenchyma, and the third inflow. 1. Introduction Nondiffuse fatty liver is considered to develop when the fat accumulation ability of hepatocytes or fat deposition becomes heterogeneous throughout the liver and is classified into the following 4 types: focal steatosis, multifocal steatosis, lobar or segmental steatosis, and focal spared lesion in fatty liver [1]. Based on imaging studies, insulin and nutrient levels in the blood flowing into the corresponding hepatic areas are considered to be causative in the frequent development of focal steatosis and focal spared lesion [2]. Some cases of focal steatosis and focal spared lesion exhibit an oval or mass-like appearance on imaging, and differentiation from liver tumors may be problematic. In this study, we performed contrast-enhanced ultrasonography (CEUS) for focal steatosis and focal spared lesions using Sonazoid (Daiichi Sankyo Pharmaceutical, Tokyo, Japan), in order to diagnose liver mass lesions, and obtained information on the hemodynamics of focal steatosis and focal spared lesions. Herein, we report these data with a review of the literature. 2. Materials and Methods The subjects were 47 patients in whom liver mass lesions were detected on abdominal ultrasonography during health check-up and underwent CEUS with Sonazoid. The findings of these patients were investigated retrospectively. These were diagnosed with focal steatosis (24 cases) or a focal spared
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